Chromatic and spatial information processing by red cones and L-type horizontal cells in the turtle retina.

Flash sensitivities to red (694 nm) and green (546 nm) light were measured intracellularly from red cones and L-type horizontal cells in the turtle retina. The horizontal cells' sensitivity to short wavelength light was significantly larger than expected from the model where horizontal cells receive input mainly from red cones. The red cone responses to chromatic stimuli were strongly dependent upon the flash colour and size. Increasing the spot size reduced the sensitivity to green relative to red and augmented the differences in kinetics between the response to red light and that evoked by green light. It was concluded that L-type horizontal cells received a short wavelength input in addition to the input from red cones. This additional green input coupled with the negative feedback pathway from horizontal cells onto red cones determined the differential spatial properties of the red cone responses to red and green test flashes.